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ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
Recognizing the increasingly stringent requirements for EMC/EMI in automotive applications, Allegro has taken the necessary steps to design devices that are capable of withstanding the effects of radiated and conducted transients. The ATS673 and ATS674 devices have been designed specifically for this purpose. Advanced circuitry on the die allows them to survive positive and negative transient pulses on both the input and output. The ATS673 and ATS674 devices retain all of the same characteristics as the ATS671 and ATS672. The devices remain true zero-speed gear tooth sensors with optimized Hall IC/magnet configuration in an SIP (single in-line package). The SIP assembly consists of a molded package that holds together a samarium cobalt magnet, a pole piece, and a true zero-speed Hall IC that has been optimized to the magnetic circuit. The sensor incorporates a single element Hall IC that switches in response to magnetic signals created by a ferrous target. The IC contains a sophisticated digital circuit designed to eliminate the detrimental effects of magnet and system offsets. Signal processing is used to provide zero-speed performance independent of air gap and also to dynamically adapt device performance to the typical operating conditions found in automotive applications, particularly cam sensing applications (reduced vibration sensitivity). High-resolution (9-bit) peak detecting DACs are used to set the adaptive switching thresholds of the devices, ensuring high accuracy even in the presence of gear eccentricity. Hysteresis in the thresholds reduces the negative effects of anomalies in the magnetic signal (such as magnetic overshoot) associated with the targets used in many automotive applications. The ATS673 and 674 also include a low bandwidth filter that increases the noise immunity and the signal to noise ratio of the sensor. Two options are available for output polarity, low over tooth (LT) and high over tooth (HT). For applications requiring absolute accuracy use the ATS674. The ATS673 should be used for targets with high wobble.
Package SE, 4-pin Through Hole
1 1. VCC 2. VOUT 3. TEST 4. GND
2
3
4
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, VCC ........................................... 28 V Reverse-Supply Voltage, VRCC ........................ -18 V Continuous Output Current, IOUT ...................20 mA Reverse-Output Current, IROUT.......................50 mA Operating Temperature Ambient, TA, Range L................ -40C to 150C Maximum Junction, TJ(max)........................165C Storage Temperature, TS .................. -65C to 170C
Features and Benefits
Tight timing accuracy over operating temperature range True zero-speed operation TPOS (True Power-On State) Air-gap-independent switchpoints High immunity to vibration Large operating air gaps Operation with supply voltages down to 3.3 V Digital output representing target profile Single-chip solution for high reliability Optimized Hall IC/magnet system AGC and reference adjust circuit Undervoltage lockout
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
ATS673LSE-DS
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
Product Selection Guide
Part Number ATS673LSETN-LT-T ATS673LSETN-LT ATS673LSETN-HT-T ATS673LSETN-HT ATS674LSETN-LT-T ATS674LSETN-LT ATS674LSETN-HT-T ATS674LSETN-HT
*Contact Allegro
Pb-free Yes - Yes - Yes - Yes -
VOUT (Over Tooth) Low
Application
Packing*
High target wobble High 13-in. reel, 450 pieces/reel Low High absolute edge detection accuracy High
for additional packing options.
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
2
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
Functional Block Diagram
V+
VCC Voltage Regulator (Analog) VREG(A) Voltage Regulator (Digital) VREG(D)
Hall Amp
Offset Adjust Temperature Coefficient Adjust
Automatic Gain Control LPF
VPROC
Offset
TC
VREF
9-Bit PDAC
9 Comp_P 0.1 F CBYPASS Continuous Update Logic Output State Clock Continuous Update Logic Comp_N Output State 9-Bit Counter Clock 9-Bit Counter Threshold Output
9 9-Bit NDAC
TPOS
VREG(A) Power-On Reset
VREG(D) Output Driver Threshold Comparator VOUT
TPOS Trim
GND (Recommended)
TEST
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
3
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
OPERATING CHARACTERISTICS Valid at TA = -40C to 150C, TJ TJ(max), over full range of AG, unless otherwise noted
Characteristic
Supply Voltage Undervoltage Lockout Supply Zener Clamp Voltage Supply Zener Current2 Supply Current Reverse Supply Current POWER-ON CHARACTERISTICS Power-On Time3 OUTPUT CHARACTERISTICS Low Output Voltage Output Zener Voltage Output Current Limit Output Leakage Current Output Rise Time Output Fall Time VOUT(Sat) VZOUT IOUTLIM IOUTOFF tr tf VOUT ISINK = 15 mA, Output = ON IOUT = 3 mA, TA = 25C Output = ON, VOUT = 12 V Output = OFF, VOUT = VCC(Max) 10/90% points; RLOAD = 500 , CLOAD = 10 pF, TA = 25C 10/90% points; RLOAD = 500 , CLOAD = 10 pF, TA = 25C Over tooth HT device option Over valley LT device option Over tooth Over valley - 30 35 - - - - - - - 200 - 57 - 0.9 0.5 HIGH LOW LOW HIGH 450 - 90 10 5 5 - - - - mV V mA A s s V V V V tPO Gear Speed < 100 rpm; VCC > VCC(Min) - - 500 s
Symbol
VCC VCCUV VZSupply IZSupply ICC IRCC
Test Conditions
Operating; TJ < TJ(Max) ICC = ICC(Max) + 3 mA, TA = 25C VSupply = 27 V Output = OFF or ON VRCC = -18 V
Min.
3.3 - 28 - 3 -
Typ.1
- - 31 - 6.5 -5
Max.
26.5 Units
V V V mA mA mA
ELECTRICAL CHARACTERISTICS
Output Polarity
Continued on the next page...
V+ VOUT(High)
Output Rise and Fall Time
%
100 90
VOUT(Low)
t+
10 0
tr
tf
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
4
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
OPERATING CHARACTERISTICS, continued Valid at TA = -40C to 150C, TJ TJ(max), over full range of AG, unless otherwise noted
Characteristic
Tooth Speed Bandwidth Operate Release
Symbol
S BW BOP BRP
Test Conditions
Tooth frequency, target generating sinusoidal signal Corresponds to output switching frequency - 3 dB ATS673 % of peak-to-peak, referenced to tooth signal, ATS674 AG < AG(Max) ATS673 % of peak-to-peak, referenced to tooth signal, ATS674 AG < AG(Max) Quantity of rising edges required to complete edge detection calibration Quantity of rising edges required to complete Automatic Gain Control calibration Quantity of rising edges required to update edge detection calibration while running after initial calibration TPOS functionality guaranteed TPOS guaranteed, output switching, running mode Output switching, running mode; valleys may be detected as teeth in this range Output switching, running mode; teeth may be detected as valleys in this range ATS673 During initial calibration; rising or falling edges, gear speed = 1000 rpm, target eccentricity ATS674 < 0.1 mm ATS673 Rising edges; after initial calibration, gear speed ATS674 = 1000 rpm, target eccentricity < 0.1 mm ATS673 Falling edges; after initial calibration, gear speed ATS674 = 1000 rpm, target eccentricity < 0.1 mm After initial calibration, AG = 1.5 mm, TA = 25C 25C.
Min.
0 - - - - -
Typ.1
- 40 40 30 50 40
Max.
8 - - - - -
Units
kHz kHz % % % %
SWITCHPOINT CHARACTERISTICS
CALIBRATION CHARACTERISTICS4 Initial Calibration AGC Disable Calibration Update CalIC CalAGC CalUPD AGTPOS AG AGEXTMIN AGEXTMAX ErrICREL - - - - - Continuous - - - - 3 3 0.5 0.4 0.8 0.6 1.6 x 10-4 3 3 - edges edges edges
PERFORMANCE CHARACTERISTICS3 TPOS Air Gap Range5 Operational Air Gap Range Extended Minimum Air Gap6 Extended Maximum Air Gap7 0.5 0.5 - 2.5 - - - - - - - 2.5 2.5 0.5 5 6 6 0.8 0.8 1.2 1.2 - mm mm mm mm deg deg deg deg deg deg deg/rpm
Relative Timing Accuracy4,8
ErrRELR
ErrRELF Phase Delay9
1Typical
ErrSREL
values are taken at VCC = 12 V and TA = 2I ZSupply(Max) is equivalent to ICCON(Max) + 3 mA. 3Using reference target 8X.
4The
term edge refers to a mechanical edge, such as the side of a gear tooth, passing under the device. Rising edge: from valley to approaching tooth. Falling edge: from tooth to approaching valley. 5The TPOS Air Gap Range is the range of installation air gaps within which the TPOS (True Power-On State) function is guaranteed to correctly detect a tooth when powered-on over a tooth and correctly detecting a valley when powered-on over a valley, using reference target 8X or equivalent, as specified in the Target/Gear Parameters for Correct TPOS Operation section in this document. 6The Extended Minimum Air Gap is a range of installation air gaps, smaller than AG (Min), within which the the device will accurately detect target features but TPOS is NOT guaranteed to be fully accurate, possibly evaluating the initial valley as a tooth. 7The Extended Maximum Air Gap is an extended range of installation air gaps, greater than AG (Max), within which the the device will accurately detect target features but TPOS is not guaranteed to be fully accurate, possibly evaluating the intiial tooth as a valley. 8Relative Timing Accuracy is the change in edge position before the resulting change in device output; for a single device, over the full Operational Air Gap Range, AG, and Operating Ambient Temperature, TA , range. 9Phase Delay is the change in edge position at detection, through the full operational Tooth Speed, S, range for a single device, and at a single ambient temperature, TA, and installation air gap, AG.
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
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ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
Air Gap Comparisons
Target (Gear)
Installation Air Gap
Extended Maximum Air Gap, AGEXTMAX
9
Sensor Device Branded Face
Operational Air Gap Range, AG TPOS Air Gap Range, AGTPOS Extended Minimum Air Gap Air Gap, AGEXTMIN
Relative Timing Accuracy
Target Mechanical Profile
V+
Sensor Output Electrical Profile -HT Option
VOUT
t ErrRELR(Max - Min) ErrRELF(Max - Min)
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
6
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Reference Target (Gear) Information
REFERENCE TARGET 8X Characteristic Outside Diameter Face Width Circular Tooth Length Circular Valley Length Tooth Whole Depth Material Symbol Do F t tv ht CRS 1018 Test Conditions Outside diameter of target Breadth of tooth, with respect to sensor Length of tooth, with respect to sensor; measured at Do Length of valley, with respect to sensor; measured at Do Typ. 120 6 23.6 23.6 5 - Units mm mm mm mm mm - Symbol Key
Branded Face of Sensor
tV
ODO
F ht
Branded Face of Sensor
Reference Target 8X
Figure 1. Configuration with Reference Target
Target/Gear Parameters for Correct TPOS Operation For TPOS to function as specified, the target must generate a minimum of 120 G difference between the magnetic field over a tooth and the field over a valley, at the maximum installation air gap. A target complying with the material and dimensions cited for the reference target 8X, generates the required 120 G differential.
The following recommendations should be followed in the design and specification of targets: * Tooth width, t 5 mm * Valley width, tv > 13 mm * Valley depth, ht > 5 mm * Tooth thickness, F 5 mm
t
Air Gap
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
7
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Characteristic Data: Electrical
Supply Current (On) Versus Ambient Temperature
11 10 11 10 VCC (V) 26.5 15.0 3.3
Supply Current (Off) Versus Ambient Temperature
ICC(OFF) (mA)
9
9 8 7 6 5 4 3 VCC (V) 26.5 15.0 3.3
ICC(ON) (mA)
8 7 6 5 4 3 -50 -25 0 25 50 75 100 125 150 175
-50
-25
0
25
50
75
100
125
150
175
TA (C)
TA (C)
Supply Current (On) Versus Supply Voltage
11 10 11 10 9 TA (C) -40 0 25 85 150
Supply Current (Off) Versus Supply Voltage
ICC(OFF) (mA)
ICC(ON) (mA)
9 8 7 6 5 4 3 0 5 10 15 20 25 30
TA (C) -40 0 25 85 150
8 7 6 5 4 3 0 5 10 15 20 25 30
VCC (V)
VCC (V)
Output Voltage (Low) Versus Ambient Temperature
500
Output Leakage Current (Off) Versus Ambient Temperature
10 8 IOUT (mA) 20 15 10
400
VOUT(SAT) (mV)
300
IOUT(OFF) (uA)
6 4 2 0
200
100
0 -50 -25 0 25 50 75 100 125 150 175
-50
-25
0
25
50
75
100
125
150
175
TA (C)
TA (C)
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
8
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Characteristic Data: Relative Timing Accuracy
ATS673 Relative Timing Accuracy Versus Air Gap Rising Mechanical Edge 1000 rpm, Relative to 0.5 mm Air Gap 0.0 -0.1
ATS673 Relative Timing Accuracy Versus Air Gap Falling Mechanical Edge 1000 rpm, Relative to 0.5 mm Air Gap 1.2 1.0 TA (C)
-40 0 25 85 150
Edge Position ()
-0.2 -0.3 -0.4 -0.5 -0.6 -0.7 -0.8
0.5
Edge Position ()
0.8 0.6 0.4 0.2 0.0
TA (C)
-40 0 25 85 150
1.0
1.5
2.0
2.5
3.0
0.5
1.0
1.5
2.0
2.5
3.0
AG (mm)
AG (mm)
ATS674 Relative Timing Accuracy Versus Air Gap Rising Mechanical Edge 1000 rpm, Relative to 0.5 mm Air Gap 0.0 -0.1
ATS674 Relative Timing Accuracy Versus Air Gap Falling Mechanical Edge 1000 rpm, Relative to 0.5 mm Air Gap 1.2 1.0
Edge Position ()
-0.2 -0.3 -0.4 -0.5 -0.6 -0.7 -0.8
Edge Position ()
TA (C)
-40 0 25 85 150
TA (C) 0.8 0.6 0.4 0.2 0.0
-40 0 25 85 150
0.5
1.0
1.5
2.0
2.5
3.0
0.5
1.0
1.5
2.0
2.5
3.0
AG (mm)
AG (mm)
Relative Timing Accuracy Versus Air Gap Rising Mechanical Edge 1.5 mm Air Gap, Relative to 0.5 mm Air Gap 0.40 0.30 0.40 0.30
Relative Timing Accuracy Versus Air Gap Falling Mechanical Edge 1.5 mm Air Gap, Relative to 0.5 mm Air Gap
Edge Position ()
0.20 0.10 0 -0.10 -0.20 -0.30 -0.40 0 500 1000 1500 2000 2500
ATS673 ATS674
Edge Position ()
0.20 0.10 0 -0.10 -0.20 -0.30 -0.40 0 500 1000 1500 2000 2500
ATS673 ATS674
Gear Speed (rpm)
Gear Speed (rpm)
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
9
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Operational Description
Assembly Description The ATS673 and ATS674 true zero-speed gear tooth sensors have a Hall IC-magnet configuration that is fully optimized to provide digital detection of gear tooth edges. This sensor is integrally molded into a plastic body that has been optimized for size, ease of assembly, and manufacturability. High operating temperature materials are used in all aspects of construction. Sensing Technology The gear tooth sensor contains a single-chip Hall effect sensor IC, a 4-pin leadframe and a specially designed rare-earth magnet. The Hall IC supports a Hall element that measures the magnetic gradient created by the passing of a ferrous object. This is illustrated in figure 2. The difference in the magnetic gradients created by teeth and valleys allows the devices to generate a digital output signal. Output After proper power is applied to the devices, they are then capable of providing digital information that is representative of the profile of a rotating gear, as illustrated in figure 3. No additional optimization is needed and minimal processing circuitry is required. This ease of use reduces design time and incremental assembly costs for most applications.
Target (Gear) High-B field Hall IC North Pole Back-Biasing magnet Plastic South Pole (A) (B) Sensor Device Pole piece (Concentrator) Low-B field Hall element Leadframe
Figure 2. Device Cross Section. Motion of the target is detected by the Hall element mounted on the Hall IC. Panel A, the presence of a tooth feature on the target is distinguished by a high magnetic flux density, B. Panel B, the presence of a valley feature is distinguished by its low magnetic flux density.
Target Mechanical Profile
Target Magnetic Profile
B+ BIN
-LT Option Sensor Output Switch State Sensor Output Electrical Profile
V+ VOUT
On
Off
On
Off
On
Off
On
Off
-HT Option Sensor Output Switch State Sensor Output Electrical Profile
Off On
V+ VOUT
Off
On
Off
On
Off
On
Figure 3. The magnetic profile reflects the geometry of the target, allowing the device to present an accurate digital output response.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
10
ATS673LSE-DS
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
TPOS (True Power-On State) Operation Under specified operating conditions, the devices are guaranteed to attain a specified output voltage polarity at power-on, in relation to the target feature nearest the device at that time. Both devices offer the options of either high or low polarity over initial tooth or valley. This polarity also applies throughout device operation. Start-Up Detection These devices provide an output polarity transition at the first mechanical edge after power-on. Undervoltage Lockout When the supply voltage falls below the undervoltage lockout level, VCCUV, the device switches to the OFF state. The device remains in that state until the voltage level is restored to to the VCC operating range. Changes in the target magnetic profile have no effect until voltage is restored. This prevents false signals caused by undervoltage conditions from propagating to the output of the sensor.
Power Supply Protection The ATS673 and ATS674 contain an on-chip regulator and can operate over a wide range of supply voltage levels. For applications using an unregulated power supply, transient protection must be added externally. For applications using a regulated supply line, EMI and RFI protection may still be required. The circuit shown in figure 5 is the basic configuration required for proper device operation. Contact Allegro field applications engineering for information on the circuitry required for compliance to various EMC specifications. Internal Electronics These devices contain a self-calibrating Hall effect IC that provides a Hall element, a temperature compensated amplifier, and offset cancellation circuitry. The IC also contains a voltage regulator that provides supply noise rejection over the operating voltage range. The Hall transducers and the electronics are integrated on the same silicon substrate by a proprietary BiCMOS process. Changes in temperature do not greatly affect this device due to the stable amplifier design and the offset rejection circuitry.
VS 1 VCC CBYPASS 0.1 F 3 ATS673/674 TEST VOUT 2 Sensor Output RPU
GND 4
Figure 5. Power Supply Protection Typical Circuit
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
11
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
AGC (Automatic Gain Control) The AGC feature is implemented by a unique patented selfcalibrating circuitry. After each power-on, the devices measure the peak-to-peak magnetic signal. The gain of the sensor is then
adjusted, keeping the internal signal amplitude constant over the air gap range of the device. This feature ensures that operational characteristics are isolated from the effects of changes in AG. The effect of AGC is shown in figure 7.
Magnetic Flux Density Versus Target Edge Position
600 500
Flux Density, B (G)
AG (mm): 1.50
400 300 200 100 0 0 10 20 30 40
2.00 2.50 3.00 3.50
50
60
70
80
90
Target Rotation ()
Internal Analog Signal after AGC Versus Target Edge Position
2.0
AG (mm):
1.5
VPROC (V)
1.50 2.00 2.50 3.00 3.50
1.0
0.5
0 0 10 20 30 40 50 60 70 80 90
Target Rotation ()
Figure 7. Effect of AGC. The upper panel shows the magnetic gradient detected at the Hall element, with no amplification. The lower panel displays the corresponding internal processed signal, VPROC. This normalized electrical signal allows optimal performance by the rest of the circuits that reference this signal.
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
12
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
Switchpoints Switchpoints in the ATS673 and ATS674 are established dynamically as a percentage of the amplitude of the signal, VPROC, after normalization with AGC. Two DACs track the peaks of VPROC (see the Update subsection). The switching thresholds are established at fixed percentages of the values held in the two DACs. The value of the thresholds has been carefully selected, where the signal is steepest and least affected by air gap variation, thus providing the most accurate and consistent switching. The low hysteresis, 10%, provides high performance over various air gaps while maintaining immunity to false switching on noise, vibration, backlash, or other transient events. Figure 8 graphically demonstrates the establishment of the switching threshold levels. Because the thresholds are established dynamically as a percentage of the peak-to-peak signal, the effect of a baseline shift is minimized.
Target Mechanical Profile
V+
100
VPROC (%)
BOP%
BRP%
0
Device State -LT option -HT option
On Off
Off On
On Off
Off On
Figure 8. Switchpoint Relationship to Thresholds.The device switches when VPROC passes a threshold level, BOP or BRP , while changing in the corresponding direction: increasing for a BOP switchpoint, and decreasing for a BRP switchpoint.
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
13
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
Update The ATS673 and ATS674 incorporate an algorithm that continuously monitors the system and updates the switching thresholds accordingly. The switchpoint for each transition is determined by the previous two transitions. Because variations are tracked
in real time, the sensor has high immunity to target run-out and retains excellent accuracy and functionality in the presence of both run-out and transient mechanical events. Figure 9 shows how the devices use historical data to provide the switching thresholds for a given edge.
(A) TEAG varying; cases such as eccentric mount, out-of-round region, normal operation position shift
V+
(B) Internal analog signal, VPROC, typically resulting in the sensor
Smaller TEAG Larger TEAG VPROC (V)
Smaller TEAG
Target
Target
Sensor
Smaller TEAG
Sensor
Larger TEAG 0
Hysteresis Band (Delimited by switchpoints) 360 Target Rotation ()
(C) Referencing the internal analog signal, VPROC, to continuously update device response
Switchpoint BOP1 BRP1 BOP2 BRP2 BOP3 BRP3 BOP4 BRP4
Determinant Peak Values Pk1, Pk2 Pk2, Pk3 Pk3, Pk4 Pk4, Pk5 Pk5, Pk6 Pk6, Pk7 Pk7, Pk8 Pk8, Pk9
V+
Pk1 Pk3
BHYS
BHYS Pk7 Pk5
BHYS
Pk9
BHYS
VPROC (V
BOP1 BRP1
BOP2 BOP3 BRP2 BRP3
BOP4 BRP4
Pk4 Pk2 BHYS BHYS
Pk6 Pk8 BHYS
BHYS
t+
Figure 9. The Continuous Update algorithm allows the Allegro sensor to immediately interpret and adapt to significant variances in the magnetic field generated by the target as a result of eccentric mounting of the target, out-of-round target shape, elevation due to lubricant build-up in journal gears, and similar dynamic application problems that affect the TEAG (Total Effective Air Gap). The algorithm is used to dynamically establish and subsequently update the device switchpoints (BOP and BRP). The hysteresis, BHYS(#x), at each target feature configuration results from this recalibration, ensuring that it remains properly proportioned and centered within the peak-to-peak range of the internal analog signal, VPROC. As shown in panel A, the variance in the target position results in a change in the TEAG. This affects the sensor as a varying magnetic field, which results in proportional changes in the internal analog signal, VPROC, shown in panel B. The Continuous Update algorithm is used to establish accurate switchpoints based on the fluctuation of VPROC, as shown in panel C.
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
14
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Sensor and Target Evaluation
Magnetic Profile In order to establish the proper operating specification for a particular sensor device and target system, a systematic evaluation of the magnetic circuit should be performed. The first step is the generation of a magnetic map of the target. By using a calibrated device, a magnetic profile of the system is made. Figure 10 is a magnetic map of the 8X reference target. A pair of curves can be derived from this map data, and be used to describe the tooth and valley magnetic field strength, B, versus the size of the air gap, AG. This allows determination of the minimum amount of magnetic flux density that guarantees operation of the sensor, so the system designer can determine the maximum allowable AG for the sensor and target system. One can also determine the TPOS air gap capabilities of the sensor by comparing the minimum tooth signal to the maximum valley signal.
Magnetic Map, Reference Target 8X with SE Package
1600 1400 1200
Flux Density,B (G)
1000 800 600 400 200 0 0 60 120 180 240 300 360
Target Rotation ()
Air Gap Versus Magnetic Field, Reference Target 8X with SE Package
1300 1200 1100 1000
Flux Density,B (G)
900 800 700 600 500 400 300 200 100 0 0 1.0 2.0 3.0 4.0 5.0 6.0 Tooth Valley
AG (mm)
Figure 10. Magnetic Data for the 8X Reference Target and SE package.
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
15
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
Accuracy While the update algorithm will allow the sensor devices to adapt to typical air gap variations, major changes in air gap can adversely affect switching performance. When characterizing sensor performance over a significant air gap range, be sure to
repower the device at each test at different air gaps. This ensures that self-calibration occurs for each installation condition. See the Operating Characteristics table and the charts in the Characteristic Data: Relative Timing Accuracy section for performance information.
Sensor Evaluation: EMC
Characterization Only Test Name* Reference Specification
AEC-Q100-002 AEC-Q100-003 ISO 7637-1 ISO 11452-7 ISO 11452-4 ISO 11452-3 ESD - Human Body Model ESD - Machine Model Conducted Transients Direct RF Injection Bulk Current Injection TEM Cell *Please contact Allegro for EMC performance
Mechanical Information
Component
Back-biasing Magnet Sensor Package Material Leads
aTemperature bIndustry
Material
Rare Earth Thermoset Epoxy Copper
Description
South pole behind IC Maximum Temperature
Value
170Ca Solder, Tin/Lead 90/10b
excursions of up to 260C for 2 minutes or less are permitted (based on delamination studies). accepted soldering techniques are acceptable for this package as long as the indicated maximum temperature is not exceeded.
Related Documents
Documents that can be found on the Allegros web site,: www.allegromicro.com: * Definition of Terms (Pub 26004) * Hall-Effect Devices: Soldering, Gluing, Potting, Encapsulating, and Lead forming (AN27703.1) * Storage of Semiconductor Devices (Pub 26011) * Hall Effect Applications Guide (Pub 27701) * Applications Note: Back-Biased Packaging Advances (SE, SG & SH versus SA & SB)
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
16
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Power Derating
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic Package Thermal Resistance Symbol RJA Test Conditions* Minimum-K PCB (single layer, single-sided, with copper limited to solder pads) Low-K PCB (single-layer, single-sided with copper limited to solder pads and 3.57 in.2 (23.03 cm2) of copper area each side) Value Units 101 77 C/W C/W
*Additional information is available on the Allegro Web site.
Power Derating Curve TJ(max) = 165C
VCC(max)
25
30
Maximum Allowable VCC (V)
20
15
Low-K PCB (RJA = 77 C/W) Minimum-K PCB (RJA = 101 C/W)
10
5
VCC(min)
0 20 40 60 80 100 120 140 160 180
1900 1800 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0 20 40
Power Dissipation Versus Ambient for Sample PCBs
Power Dissipation, PD (m W)
Mi (R nim um J A= 10 K P 1 CB C/ W )
L (R owK J A = PC 77 B C /W
)
60
80 100 120 140 Temperature, TA (C)
160
180
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
17
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
The device must be operated below the maximum junction temperature of the device, TJ(max). Under certain combinations of peak conditions, reliable operation may require derating supplied power or improving the heat dissipation properties of the application. This section presents a procedure for correlating factors affecting operating TJ. (Thermal data is also available on the Allegro MicroSystems Web site.) The Package Thermal Resistance, RJA, is a figure of merit summarizing the ability of the application and the device to dissipate heat from the junction (die), through all paths to the ambient air. Its primary component is the Effective Thermal Conductivity, K, of the printed circuit board, including adjacent devices and traces. Radiation from the die through the device case, RJC, is relatively small component of RJA. Ambient air temperature, TA, and air motion are significant external factors, damped by overmolding. The effect of varying power levels (Power Dissipation, PD), can be estimated. The following formulas represent the fundamental relationships used to estimate TJ, at PD. PD = VIN x IIN T = PD x RJA TJ = TA + T (1) (2) (3)
Example: Reliability for VCC at TA = 150C, package SE, using minimum-K PCB. Observe the worst-case ratings for the device, specifically: RJA = 101C/W, TJ(max) = 165C, VCC(max) = 26.5 V, and ICC(max) = 11 mA. Note that ICC(max) at TA = 150C is lower than the ICC(max) at TA = 25C given in the Operating Characteristics table. Calculate the maximum allowable power level, PD(max). First, invert equation 3: Tmax = TJ(max) - TA = 165 C - 150 C = 15 C This provides the allowable increase to TJ resulting from internal power dissipation. Then, invert equation 2: PD(max) = Tmax / RJA = 15C / 101 C/W = 91 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) / ICC(max) = 91 mW / 11 mA = 8.3 V The result indicates that, at TA, the application and device can dissipate adequate amounts of heat at voltages VCC(est). Compare VCC(est) to VCC(max). If VCC(est) VCC(max), then reliable operation between VCC(est) and VCC(max) requires enhanced RJA. If VCC(est) VCC(max), then operation between VCC(est) and VCC(max) is reliable under these conditions.
For example, given common conditions such as: TA= 25C, VIN = 12 V, IIN = 4 mA, and RJA = 140 C/W, then: PD = VIN x IIN = 12 V x 4 mA = 48 mW T = PD x RJA = 48 mW x 140 C/W = 7C TJ = TA + T = 25C + 7C = 32C A worst-case estimate, PD(max), represents the maximum allowable power level, without exceeding TJ(max), at a selected RJA and TA.
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
18
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications Package SE, 4-Pin SIP
7 .276
C
10
.394
E
3.3 .130
B
4.9 6.2 .244 20.95 .825
.193
A 1.3 .051
0.38 .015
1.08 .043
11.6 .457
1
2
3
4
A
D
0.6 .240 1.27 .050 2 .079
Dimensions in millimeters. Untoleranced dimensions are nominal. U.S. Customary dimensions (in.) in brackets, for reference only A Dambar removal protrusion
B Metallic protrusion, electrically connected to pin 4 and substrate (both sides) C Active Area Depth 0.43 mm [.017] D Thermoplastic Molded Lead Bar for alignment during shipment E Hall element (size not to scale)
ATS673LSE-DS
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
19
ATS673 and ATS674
Self-Calibrating TPOS Gear Tooth Sensor Optimized for Automotive Cam Sensing Applications
The products described herein are manufactured under one or more of the following U.S. patents: 5,045,920; 5,264,783; 5,442,283; 5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; 6,297,627; 6,525,531; and other patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro products are not authorized for use as critical components in life-support devices or systems without express written approval. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. Copyright (c) 2005, Allegro MicroSystems, Inc.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
20
ATS673LSE-DS

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